This invention relates to a servo control system for controlling multiple motors.
A conventional servo control system will be described by FIGS. 8 and 9 shown in JP-A-8-237994. In FIGS. 8 and 9, in the servo control system, plural servo drivers 2-1 to 2-3 . . . corresponding to plural motors 1-1 to 1-3 . . . , a power source 3, a host controller 4, and a back panel 5 are accommodated in a rack 6.
The servo drivers 2 perform driving control of servo motors etc. and are independent of one another, and connectors (not shown) for connecting the corresponding motors are provided in the front of the servo drivers 2 and connection parts (not shown) for connection to the back panel 5 are provided in the back.
The power source 3 supplies electric power to each the servo driver 2-1 to 2-3 . . . , and the electric power is supplied through a power line 5a provided in the back panel 5.
The host controller 4 performs control of the whole apparatus and is connected to each the servo driver 2-1 to 2-3 . . . through a line 5b for LAN provided in the back panel 5.
The back panel 5 makes connections mutually among each the servo driver 2-1 to 2-3 . . . , the power source 3 and the host controller 4, and the power line 5a and the line 5b for LAN used mutually are provided. Plural connection parts 5c connected to the connection parts (not shown) provided in the back of the servo drivers 2 are provided in the back panel 5.
The rack 6 accommodates the servo drivers 2, the power source 3, the host controller 4 and the back panel 5, and a radiating fin 7 is provided in the bottom of the rack 6 and the back panel 5 is provided in the rear of the inside of the rack 6, and the connection parts (not shown) of the servo drivers 2 are coupled to the connection parts 5c of the back panel 5 by inserting the servo drivers 2 into the rack 6 from the front.
Since the servo control system is constructed as described above, crossover wiring among the servo drivers 2-1 to 2-3 . . . can be omitted by providing the power line 5a common to each the servo driver 2-1 to 2-3 . . . in the back panel 5.
Also, since each the servo driver 2-1 to 2-3 . . . is connected to the host controller 4 by the line 5b for LAN provided in the back panel 5, wiring by one servo driver becomes unnecessary.
By the way, the servo control system constructed as described above does not make reference to a technique of processing regenerative electric power from the motors 1-1 to 1-3 . . . . As such regenerative electric power processing, for example, as described in JP-A-8-289591 (see FIG. 6), in the case that a configuration for forming an output of a power source 3 into DC and connecting a capacitor to said output is adopted, when motors 1-1 to 1-3 . . . . become a regenerative state, regenerative electric power is generated from the motors 1-1 to 1-3 . . . and the regenerative electric power is stored in the capacitor through servo drivers 1-1 to 1-3 . . . .
However, since said capacitor is placed intensively, all the regenerative energy cannot be stored in the capacitor in addition of the motors 1 with an increase in the number of control shafts, change in rated capacity of the motor 1-1 etc. with an increase in a load, use with high regenerative frequency. Thus, the regenerative energy incapable of being stored is consumed by a regenerative resistor, but it is not desirable from the viewpoint of effective use of the energy.
On the other hand, in the case that a capacitor capacity is determined assuming usage in which regenerative energy is large with respect to all the motors 1-1 to 1-3 . . . , there was a problem that there is too room in a capacitance of a capacitor and the capacitor becomes large-scale more than necessary when the number of control shafts of the motors 1-1 to 1-3 . . . decreases or regenerative electric power generated from the motors 1-1 to 1-3 . . . is small.
On the contrary, when an inverter for regeneration for regenerating the regenerative electric power to an AC power source is used, there was a problem that the servo control system becomes complicated and large-scale.
This invention is implemented to solve the problems, and an object of the invention is to provide a servo control system capable of flexibly adjusting a capacitance of a capacitor connected to a DC bus according to the number of motors, motor use conditions and so on.
A servo control system according to the invention has a plurality of motors for driving a plurality of controlled targets, a plurality of drive units having a first connection part, for driving the motors, a control unit having a second connection part, for receiving a command from a host controller and sending a command to the drive unit, a rack including a back panel having a connected part for removably electrically connecting to the first and second connection parts, the rack accommodating the control unit and the drive unit, and a DC voltage conversion part for converting an AC voltage as an input into a DC voltage as an output, the DC voltage conversion part disposed in the back panel, in which the drive unit has a capacitor having a predetermined capacitance value determined based on a rated capacity of the motor driven by the drive unit and connected in parallel with an output of the DC voltage conversion part and an inverter part for converting a DC voltage into an AC voltage based on a command and the capacitor has a capacitance value in which an allowable ripple current is larger than a ripple current flowing through the capacitor at a time of a rated load of the motor and electric power is supplied to the motor with respect to an instantaneous power failure of predetermined time of the AC voltage.
The servo control system according to another aspect of the invention, has a capacitor unit having an add-on capacitor connected in parallel with the capacitor and having a third connection part removably electrically connected to the connected part of the back panel.
A servo control system according still another aspect of the invention, has a plurality of motors for driving a plurality of controlled targets, a drive unit having a first connection part, for driving the motors, a control unit having a second connection part, for receiving a command from a host controller sending a command to the drive unit, rack including a back panel having a-connected part for removable electrically connecting to the first and second connection parts, the rack accommodating the control unit and the dive unit, a DC voltage conversion part for converting an AC voltage as an input into a DC voltage as an output, the DC voltage conversion part disposed voltage detection means for generating a signal when a DC voltage value of the DC voltage conversion part reaches a predetermined value, switching means connected to an output of the DC voltage conversion part through a resistor, the switching means for performing on-off control based on the presence or absence of a signal from the voltage detection means, first calculation means for calculating consumption energy consumed in the resistor based on the on time of the switching means and the DC voltage value, second calculation means for calculating storage energy stored in the capacitor and the add-on capacitor based on a predetermined voltage rise value of the DC voltage of the DC voltage conversion part and a capacitance value of the total sum of the capacitor and the add-on capacitor and for comparing a value of the consumption energy with a value of the storage energy, and display means for displaying a result of the comparison means in which the drive unit has a capacitor having a predetermined capacitance value determined based on a rated capacity of the motor driven by the drive unit and connected in parallel with an output of the DC voltage conversion part and in inverter part for converting a DC voltage into an AC voltage based on a command.
The servo control system according to further another aspect of the invention, has a capacitor unit having an add-on capacitor connected in parallel with the capacitor and having a third connection part removably electrically connected to the connected part of the back panel, third calculation means, calculating storage energy stored in the capacitor and the add-on capacitor based on a predetermined voltage rise value of the DC voltage of the DC voltage conversion part and a capacitance value of the total sum of the capacitor and the add-on capacitor and for comparing a value of the consumption energy with a value of the storage energy, in place of the second calculation means, and display means for displaying the capacitance value.
The servo control system according to still another aspect of the invention, has identification number generation means for detecting that the first connection part of the drive unit and the third connection part of the capacitor unit are electrically connected to the connected part and for generating identification numbers associated with capacitance values of the capacitors provided in the drive unit and the capacitor unit, detection means for detecting an identification number of the identification number generation means, fourth calculation means calculating the total sum of capacitance values of the capacitor and the add-on capacitor from the identification number of the detection means and for calculating the storage energy value running short and calculating a capacitance value of a capacitor to be added when the consumption energy value obtained by the first calculation means is higher, and display means for displaying the capacitance value.